In typical continuous production of wires and/or rods from materials such as metals, continuous rolling processes are widely used for working metal materials as the workpiece, using a rolling mill roll providing rolling section[s], namely, molding groove[s], on its outer circumferential face.
A rolling mill machine, in which one end of its roll shaft connects to a rotor shaft of an electric motor, is used for such rolling mill processes. This type of rolling mill machine is called an overhung type rolling mill machine.
In continuous rolling processes using such rolling mill machines, in order to make the surface of the products (wires and/or rods) smooth, a rolling mill roll made of cemented carbide is removably attached onto the outer circumference of the roll shaft. (For example, see Patent Document 1.)
FIG. 5 shows an example of this overhung type rolling mill machine.
This rolling machine 1,                is formed of materials such as steel,        has a roll shaft 2 having an approximately cylindrical shape which goes along the direction of an axis L, and        is an overhung type rolling mill machine 1 in which a one end side (left side in FIG. 5) of the roll shaft 2 connects to a rotor axis (not shown in FIG. 5).        
A reduced diameter end section 4 formed in cylindrical tiers, is located at an other end side, (right side in FIG. 5) of the roll shaft 2.
A tapered shaft section 3 is located on the one end side of the reduced diameter end section 4. The diameter of the tapered shaft section 3 becomes gradually smaller in a direction of the other end side.
A tapered sleeve 5 having a tapered hole 6 able to fit with the tapered shaft section 3, is inserted from the other end side of the tapered shaft section 3.
The outer circumferential face of the tapered sleeve 5 is a cylindrical face parallel to an axis L.
The thickness of the tapered sleeve 5 decreases gradually in a direction of the one end side.
Also, an inserting hole 7, which goes coaxially along the taper hole 6, is bored on the other end side of the tapered sleeve 5. The reduced diameter end section 4 of the roll shaft 2 is inserted into the inserting hole 7.
A rolling mill roll 8 having an approximate ring shape integrally formed of cemented carbide is mounted on the outer circumferential face of the tapered sleeve 5.
A rolling mill section 9;                is provided on the outer circumferential face of the rolling mill roll 8,        is located at the middle length position of this rolling mill roll 8 in a direction of the axis L, and        has a semicircular shape concavely curved radially inward in a cross-section view.        
The inner circumferential face of the rolling mill roll 8 is a cylindrical face parallel to the axis L.
Moving the tapered sleeve 5 mounted on the roll shaft 2 toward the one end side, the tapered shaft section 3 makes the tapered sleeve 5 expand and reshape radially outward.
Then, the tapered sleeve 5 presses the inner circumferential face of the rolling mill roll 8 and also makes it expand radially outward. Therefore the rolling mill roll 8 is fixed on the outer circumferential face of the tapered sleeve 5.
A taper fitting method fixes the tapered sleeve 5 on the tapered shaft section 3. Thus, the rolling machine 1 comprises the roll shaft 2, the tapered sleeve 5 and the rolling mill roll 8 as a single unit.
Different from the aforementioned rolling mill roll 8 integrally formed of cemented carbide, a rolling mill, in which the use of expensive cemented carbide on the rolling mill is reduced in order to cut down its total production cost, is known.
In such rolling mill, only a ring shaped outer circumferential face, which comes in contact with a workpiece while a rolling mill process is in operation, is made of cemented carbide.
To assemble this rolling mill,                a ring made of cast iron is wedged into the inner circumferential region of the above cemented carbide ring:        a steel material having a cylindrical shape is cooled, and then inserted into the inner circumferential region of the above cast iron ring:        and afterward        these components are heated for integrating them as a single unit.        
(For an example, see Patent Document 2.)    [Patent Document 1]    Japanese Patent No. JP 3116040    [Patent Document 2]    Japanese Examined Patent Application JP H03-000154B2